Extended abstract
Introduction: Due to their aggressive and competitive habits, weeds inhibit the growth of valuable plants. Interference in plants includes environmental competition and allelopathy (Autotoxicity and hetrotoxicity). In hetrotoxicity, chemical compounds released from plants are able to effect the neighboring plants. Proper management of weeds and the exploitation of their hetrotoxicity potential can reduce losses caused by weeds. This could also represent an effective step towards the reduction of the use of herbicides. Therefore, the purpose of this study was to evaluate the effect of hetrotoxicity potential of aqueous extract of various organs of Malva sylvestris L. weed on traits of germination and photosynthetic pigments of Echinochloa crus-galli L.
Material and Methods: An experiment was conducted to evaluate the effect of hetrotoxicity potential of aqueous extract of Malva sylvestris  L. weed including the stem, leaf and flower as well as their mixture on traits of germination and photosynthetic pigments of Echinochloa crus-galli L. as a completely randomized design in three replications in Weeds Science Laboratory of Gonbad Kavous University in 2017. For this experiment, aerial parts of M. sylvestris were first collected at the flowering stage from Ramian field. They were subsequently separated with great care and were powdered. Then from them, 5% suspensions (weight/volume) were prepared, using distilled water. Finally, the extract of each organ of M. sylvestris was added to Petri dishes containing E. crus-galli seeds. After the 7^th day, traits such as rate and percentage of germination, radical and shoot elongation, vigor index, total content of chlorophyll a and b and carotenoids were measured.

Results: The results showed that various organs of M. sylvestris and their mixture had different inhibitory effects on traits of germination and seedling length of E. crus-galli weed. The highest inhibition effects on rate and germination percentage and elongation of radical and shoot of E. crus-galli were obtained using leaf extract of M. sylvestris about 64.04, 64.37, 87.69, 62.81%. In this study, radical length is more affected under hetrotoxic compounds of various organs of M. sylvestris, as compared with shoot length. Based on the results, various organs of M. sylvestris and their mixture also have different inhibitory effects on chlorophyll and carotenoid content of E. crus-galli weed. It seems that the differential effects among different organs of M. sylvestris are a function of the threshold concentration of allelochemicals to hetrotoxic compounds of the organs, which causes various response by E. crus-galli.
Conclusion: Given the evidence for the effect of hetrotoxicity potential of various organs of M. sylvestris on traits of germination and pigments of chlorophyll and carotenoid of E. crus-galli and huge biomass generated, it is advisable to exploit allelochemical compounds of this plant as bio-herbicides.
 

 
Highlights:
1- Study of the the effect of hetrotoxic potential of Malva sylvestris weed on germination characteristics and photosynthetic pigments of Echinochloa crus-galli in Ramian field.
2- E. crus-galli weed exhibits great sensitivity to hetrotoxic compounds of various organs of M. sylvestris,  especially the leaves.
3- Allelopathic characteristics of M. sylvestris weed have huge potentials for the production of bio-herbicides.